In the manufacture of a dynamoelectric machine, it is necessary that a rotatable assembly thereof, such as a shaft and rotor for instance, be properly aligned both radially and axially with a cooperating stator or stationary assembly of the dynamoelectric machine. If radially misaligned, an eccentric air gap between the rotatable assembly and stator may result thereby to effect a non-uniform flux path with poor electric efficiencies and the mechanical deficiency of vibration, and if axially misaligned, an undesirably great amount of axial rotor thrust is produced. Of course, it is also necessry that bearing means carried by an end frame construction of the dynamoelectric machine be aligned and in suitable journaling engagement with the rotatable assembly in order to provide proper longevity for such bearing means.
In the past, several different methods of assemblying dynamoelectric machines have been utilized to effect the abovementioned proper radial and axial alignment of the rotatable assembly, stator and end frames of the dynamoelectric machine. For example, through-bolts have been used to interconnect the stator and end frames of a dynamoelectric machine with the rotatable assembly thereof journaled in the end frames; however, one of the disadvantageous or undesirable features of this construction is believed to be that rather close tolerances were required to attain proper alignment of the dynamoelectric machine components, and maintaining close tolerances manifestly results in increased machining and assembly costs of manufacture. Another past method of assembling dynamoelectric machines was to employ an oversized dummy rotatable assembly to effect the necessary alignment between the stator and end plate and thereafter substitute an actual rotatable assembly for the dummy rotatable assembly; however, one of the disadvantageous or undesirable features of this method of construction is believed to be that it was limited to "unit bearing" type machines wherein the rotatable assembly is supported in only one end frame. As a result, this method was unavailable for use in the greater majority of dynamoelectric machines wherein the rotatable assembly is supported in oppositely disposed end frames.
In U.S. Pat. No. 3,165,816 shims were disposed between the rotatable assembly and stator to effect proper radial alignment therebetween, and a rocker arm mechanism was employed to maintain the rotatable assembly and stator in their proper assembled positions while an adhesive such as a thermosetting resin, was applied to bond together the stator and opposite end plates in which the rotatable assembly was journaled.
In U.S. Pat. No. 3,705,994 another method of assembling dynamoelectric machines is disclosed wherein the opposite end frames thereof were welded to beams carried by the stator while the rotatable assembly was supported therein; however, one of the disadvantageous or undesirable features of this method is believed to be that the welds themselves, upon cooling, created stresses which tend to effect misalignment, as well known to the art.
In U.S. Pat. No. 2,892,225, there is disclosed a method of casting metal wherein molten metal in predetermined amounts are delivered directly from a source or furnace therefor to a casting ladle disposed adjacent to a mold, and the molten metal is then poured from the ladel into the mold. One of the disadvantageous or undesirable features of this past method of casting metal is believed to be that it was necessary not only to maintain the molten metal in the furnace at a predetermined temperature proper for the casting operations but it was also necessary to maintain such predetermined temperature of the molten metal as it was delivered from the source to the casting ladle. Since some metals, such as zinc, lead, aluminum or the like and various alloys thereof cool or solidify at a rather rapid rate, the time factor involved in delivering such molten metal from the source thereof to the casting ladle and casting it may, of course, be critical and relatively short.
The principle object of the present invention is to provide a method for casting a metal which overcome the aforementioned disadvantageous or undesirable features of the past apparatus, and this, as well as other objects and advantageous features of the present invention, will be in part apparent and in part pointed out in the specification which follows.